<html>
    <head>
        <title>
            选择器
        </title>
        <link rel="stylesheet" type="text/css" href="选择器.css">
    </head>
    <body>
        <div id="div1">id选择器</div>
        <div class="div2">class选择器</div>
        <div id="div3">组合选择器</div>
        <div class="c4"></div>
        <div id="div4">
            <p>
              12345
            </p>
            <div id="div5">
                <p>
               23456
                </p>
            </div>
        </div>
        <input type="text" name="1" id="username">
        <input type="password" name="2" id="password">
        <br>
        <br>
        <a href="www.baidu.com" target="_blank">去百度</a>
    </body>

    <table >
        <tr>
            <td>
            1
            </td>
            <td>
             2
            </td>   
        </tr>
        <tr>
        <td>
        3
        </td>
        <td>
        4
        </td>        
        </tr>
       


    </table>
</html>